xref: /linux/security/keys/keyctl.c (revision 95e9fd10f06cb5642028b6b851e32b8c8afb4571)
1 /* Userspace key control operations
2  *
3  * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/slab.h>
16 #include <linux/syscalls.h>
17 #include <linux/key.h>
18 #include <linux/keyctl.h>
19 #include <linux/fs.h>
20 #include <linux/capability.h>
21 #include <linux/string.h>
22 #include <linux/err.h>
23 #include <linux/vmalloc.h>
24 #include <linux/security.h>
25 #include <asm/uaccess.h>
26 #include "internal.h"
27 
28 static int key_get_type_from_user(char *type,
29 				  const char __user *_type,
30 				  unsigned len)
31 {
32 	int ret;
33 
34 	ret = strncpy_from_user(type, _type, len);
35 	if (ret < 0)
36 		return ret;
37 	if (ret == 0 || ret >= len)
38 		return -EINVAL;
39 	if (type[0] == '.')
40 		return -EPERM;
41 	type[len - 1] = '\0';
42 	return 0;
43 }
44 
45 /*
46  * Extract the description of a new key from userspace and either add it as a
47  * new key to the specified keyring or update a matching key in that keyring.
48  *
49  * The keyring must be writable so that we can attach the key to it.
50  *
51  * If successful, the new key's serial number is returned, otherwise an error
52  * code is returned.
53  */
54 SYSCALL_DEFINE5(add_key, const char __user *, _type,
55 		const char __user *, _description,
56 		const void __user *, _payload,
57 		size_t, plen,
58 		key_serial_t, ringid)
59 {
60 	key_ref_t keyring_ref, key_ref;
61 	char type[32], *description;
62 	void *payload;
63 	long ret;
64 	bool vm;
65 
66 	ret = -EINVAL;
67 	if (plen > 1024 * 1024 - 1)
68 		goto error;
69 
70 	/* draw all the data into kernel space */
71 	ret = key_get_type_from_user(type, _type, sizeof(type));
72 	if (ret < 0)
73 		goto error;
74 
75 	description = strndup_user(_description, PAGE_SIZE);
76 	if (IS_ERR(description)) {
77 		ret = PTR_ERR(description);
78 		goto error;
79 	}
80 
81 	/* pull the payload in if one was supplied */
82 	payload = NULL;
83 
84 	vm = false;
85 	if (_payload) {
86 		ret = -ENOMEM;
87 		payload = kmalloc(plen, GFP_KERNEL | __GFP_NOWARN);
88 		if (!payload) {
89 			if (plen <= PAGE_SIZE)
90 				goto error2;
91 			vm = true;
92 			payload = vmalloc(plen);
93 			if (!payload)
94 				goto error2;
95 		}
96 
97 		ret = -EFAULT;
98 		if (copy_from_user(payload, _payload, plen) != 0)
99 			goto error3;
100 	}
101 
102 	/* find the target keyring (which must be writable) */
103 	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
104 	if (IS_ERR(keyring_ref)) {
105 		ret = PTR_ERR(keyring_ref);
106 		goto error3;
107 	}
108 
109 	/* create or update the requested key and add it to the target
110 	 * keyring */
111 	key_ref = key_create_or_update(keyring_ref, type, description,
112 				       payload, plen, KEY_PERM_UNDEF,
113 				       KEY_ALLOC_IN_QUOTA);
114 	if (!IS_ERR(key_ref)) {
115 		ret = key_ref_to_ptr(key_ref)->serial;
116 		key_ref_put(key_ref);
117 	}
118 	else {
119 		ret = PTR_ERR(key_ref);
120 	}
121 
122 	key_ref_put(keyring_ref);
123  error3:
124 	if (!vm)
125 		kfree(payload);
126 	else
127 		vfree(payload);
128  error2:
129 	kfree(description);
130  error:
131 	return ret;
132 }
133 
134 /*
135  * Search the process keyrings and keyring trees linked from those for a
136  * matching key.  Keyrings must have appropriate Search permission to be
137  * searched.
138  *
139  * If a key is found, it will be attached to the destination keyring if there's
140  * one specified and the serial number of the key will be returned.
141  *
142  * If no key is found, /sbin/request-key will be invoked if _callout_info is
143  * non-NULL in an attempt to create a key.  The _callout_info string will be
144  * passed to /sbin/request-key to aid with completing the request.  If the
145  * _callout_info string is "" then it will be changed to "-".
146  */
147 SYSCALL_DEFINE4(request_key, const char __user *, _type,
148 		const char __user *, _description,
149 		const char __user *, _callout_info,
150 		key_serial_t, destringid)
151 {
152 	struct key_type *ktype;
153 	struct key *key;
154 	key_ref_t dest_ref;
155 	size_t callout_len;
156 	char type[32], *description, *callout_info;
157 	long ret;
158 
159 	/* pull the type into kernel space */
160 	ret = key_get_type_from_user(type, _type, sizeof(type));
161 	if (ret < 0)
162 		goto error;
163 
164 	/* pull the description into kernel space */
165 	description = strndup_user(_description, PAGE_SIZE);
166 	if (IS_ERR(description)) {
167 		ret = PTR_ERR(description);
168 		goto error;
169 	}
170 
171 	/* pull the callout info into kernel space */
172 	callout_info = NULL;
173 	callout_len = 0;
174 	if (_callout_info) {
175 		callout_info = strndup_user(_callout_info, PAGE_SIZE);
176 		if (IS_ERR(callout_info)) {
177 			ret = PTR_ERR(callout_info);
178 			goto error2;
179 		}
180 		callout_len = strlen(callout_info);
181 	}
182 
183 	/* get the destination keyring if specified */
184 	dest_ref = NULL;
185 	if (destringid) {
186 		dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
187 					   KEY_WRITE);
188 		if (IS_ERR(dest_ref)) {
189 			ret = PTR_ERR(dest_ref);
190 			goto error3;
191 		}
192 	}
193 
194 	/* find the key type */
195 	ktype = key_type_lookup(type);
196 	if (IS_ERR(ktype)) {
197 		ret = PTR_ERR(ktype);
198 		goto error4;
199 	}
200 
201 	/* do the search */
202 	key = request_key_and_link(ktype, description, callout_info,
203 				   callout_len, NULL, key_ref_to_ptr(dest_ref),
204 				   KEY_ALLOC_IN_QUOTA);
205 	if (IS_ERR(key)) {
206 		ret = PTR_ERR(key);
207 		goto error5;
208 	}
209 
210 	/* wait for the key to finish being constructed */
211 	ret = wait_for_key_construction(key, 1);
212 	if (ret < 0)
213 		goto error6;
214 
215 	ret = key->serial;
216 
217 error6:
218  	key_put(key);
219 error5:
220 	key_type_put(ktype);
221 error4:
222 	key_ref_put(dest_ref);
223 error3:
224 	kfree(callout_info);
225 error2:
226 	kfree(description);
227 error:
228 	return ret;
229 }
230 
231 /*
232  * Get the ID of the specified process keyring.
233  *
234  * The requested keyring must have search permission to be found.
235  *
236  * If successful, the ID of the requested keyring will be returned.
237  */
238 long keyctl_get_keyring_ID(key_serial_t id, int create)
239 {
240 	key_ref_t key_ref;
241 	unsigned long lflags;
242 	long ret;
243 
244 	lflags = create ? KEY_LOOKUP_CREATE : 0;
245 	key_ref = lookup_user_key(id, lflags, KEY_SEARCH);
246 	if (IS_ERR(key_ref)) {
247 		ret = PTR_ERR(key_ref);
248 		goto error;
249 	}
250 
251 	ret = key_ref_to_ptr(key_ref)->serial;
252 	key_ref_put(key_ref);
253 error:
254 	return ret;
255 }
256 
257 /*
258  * Join a (named) session keyring.
259  *
260  * Create and join an anonymous session keyring or join a named session
261  * keyring, creating it if necessary.  A named session keyring must have Search
262  * permission for it to be joined.  Session keyrings without this permit will
263  * be skipped over.
264  *
265  * If successful, the ID of the joined session keyring will be returned.
266  */
267 long keyctl_join_session_keyring(const char __user *_name)
268 {
269 	char *name;
270 	long ret;
271 
272 	/* fetch the name from userspace */
273 	name = NULL;
274 	if (_name) {
275 		name = strndup_user(_name, PAGE_SIZE);
276 		if (IS_ERR(name)) {
277 			ret = PTR_ERR(name);
278 			goto error;
279 		}
280 	}
281 
282 	/* join the session */
283 	ret = join_session_keyring(name);
284 	kfree(name);
285 
286 error:
287 	return ret;
288 }
289 
290 /*
291  * Update a key's data payload from the given data.
292  *
293  * The key must grant the caller Write permission and the key type must support
294  * updating for this to work.  A negative key can be positively instantiated
295  * with this call.
296  *
297  * If successful, 0 will be returned.  If the key type does not support
298  * updating, then -EOPNOTSUPP will be returned.
299  */
300 long keyctl_update_key(key_serial_t id,
301 		       const void __user *_payload,
302 		       size_t plen)
303 {
304 	key_ref_t key_ref;
305 	void *payload;
306 	long ret;
307 
308 	ret = -EINVAL;
309 	if (plen > PAGE_SIZE)
310 		goto error;
311 
312 	/* pull the payload in if one was supplied */
313 	payload = NULL;
314 	if (_payload) {
315 		ret = -ENOMEM;
316 		payload = kmalloc(plen, GFP_KERNEL);
317 		if (!payload)
318 			goto error;
319 
320 		ret = -EFAULT;
321 		if (copy_from_user(payload, _payload, plen) != 0)
322 			goto error2;
323 	}
324 
325 	/* find the target key (which must be writable) */
326 	key_ref = lookup_user_key(id, 0, KEY_WRITE);
327 	if (IS_ERR(key_ref)) {
328 		ret = PTR_ERR(key_ref);
329 		goto error2;
330 	}
331 
332 	/* update the key */
333 	ret = key_update(key_ref, payload, plen);
334 
335 	key_ref_put(key_ref);
336 error2:
337 	kfree(payload);
338 error:
339 	return ret;
340 }
341 
342 /*
343  * Revoke a key.
344  *
345  * The key must be grant the caller Write or Setattr permission for this to
346  * work.  The key type should give up its quota claim when revoked.  The key
347  * and any links to the key will be automatically garbage collected after a
348  * certain amount of time (/proc/sys/kernel/keys/gc_delay).
349  *
350  * If successful, 0 is returned.
351  */
352 long keyctl_revoke_key(key_serial_t id)
353 {
354 	key_ref_t key_ref;
355 	long ret;
356 
357 	key_ref = lookup_user_key(id, 0, KEY_WRITE);
358 	if (IS_ERR(key_ref)) {
359 		ret = PTR_ERR(key_ref);
360 		if (ret != -EACCES)
361 			goto error;
362 		key_ref = lookup_user_key(id, 0, KEY_SETATTR);
363 		if (IS_ERR(key_ref)) {
364 			ret = PTR_ERR(key_ref);
365 			goto error;
366 		}
367 	}
368 
369 	key_revoke(key_ref_to_ptr(key_ref));
370 	ret = 0;
371 
372 	key_ref_put(key_ref);
373 error:
374 	return ret;
375 }
376 
377 /*
378  * Invalidate a key.
379  *
380  * The key must be grant the caller Invalidate permission for this to work.
381  * The key and any links to the key will be automatically garbage collected
382  * immediately.
383  *
384  * If successful, 0 is returned.
385  */
386 long keyctl_invalidate_key(key_serial_t id)
387 {
388 	key_ref_t key_ref;
389 	long ret;
390 
391 	kenter("%d", id);
392 
393 	key_ref = lookup_user_key(id, 0, KEY_SEARCH);
394 	if (IS_ERR(key_ref)) {
395 		ret = PTR_ERR(key_ref);
396 		goto error;
397 	}
398 
399 	key_invalidate(key_ref_to_ptr(key_ref));
400 	ret = 0;
401 
402 	key_ref_put(key_ref);
403 error:
404 	kleave(" = %ld", ret);
405 	return ret;
406 }
407 
408 /*
409  * Clear the specified keyring, creating an empty process keyring if one of the
410  * special keyring IDs is used.
411  *
412  * The keyring must grant the caller Write permission for this to work.  If
413  * successful, 0 will be returned.
414  */
415 long keyctl_keyring_clear(key_serial_t ringid)
416 {
417 	key_ref_t keyring_ref;
418 	long ret;
419 
420 	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
421 	if (IS_ERR(keyring_ref)) {
422 		ret = PTR_ERR(keyring_ref);
423 
424 		/* Root is permitted to invalidate certain special keyrings */
425 		if (capable(CAP_SYS_ADMIN)) {
426 			keyring_ref = lookup_user_key(ringid, 0, 0);
427 			if (IS_ERR(keyring_ref))
428 				goto error;
429 			if (test_bit(KEY_FLAG_ROOT_CAN_CLEAR,
430 				     &key_ref_to_ptr(keyring_ref)->flags))
431 				goto clear;
432 			goto error_put;
433 		}
434 
435 		goto error;
436 	}
437 
438 clear:
439 	ret = keyring_clear(key_ref_to_ptr(keyring_ref));
440 error_put:
441 	key_ref_put(keyring_ref);
442 error:
443 	return ret;
444 }
445 
446 /*
447  * Create a link from a keyring to a key if there's no matching key in the
448  * keyring, otherwise replace the link to the matching key with a link to the
449  * new key.
450  *
451  * The key must grant the caller Link permission and the the keyring must grant
452  * the caller Write permission.  Furthermore, if an additional link is created,
453  * the keyring's quota will be extended.
454  *
455  * If successful, 0 will be returned.
456  */
457 long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
458 {
459 	key_ref_t keyring_ref, key_ref;
460 	long ret;
461 
462 	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
463 	if (IS_ERR(keyring_ref)) {
464 		ret = PTR_ERR(keyring_ref);
465 		goto error;
466 	}
467 
468 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_LINK);
469 	if (IS_ERR(key_ref)) {
470 		ret = PTR_ERR(key_ref);
471 		goto error2;
472 	}
473 
474 	ret = key_link(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));
475 
476 	key_ref_put(key_ref);
477 error2:
478 	key_ref_put(keyring_ref);
479 error:
480 	return ret;
481 }
482 
483 /*
484  * Unlink a key from a keyring.
485  *
486  * The keyring must grant the caller Write permission for this to work; the key
487  * itself need not grant the caller anything.  If the last link to a key is
488  * removed then that key will be scheduled for destruction.
489  *
490  * If successful, 0 will be returned.
491  */
492 long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
493 {
494 	key_ref_t keyring_ref, key_ref;
495 	long ret;
496 
497 	keyring_ref = lookup_user_key(ringid, 0, KEY_WRITE);
498 	if (IS_ERR(keyring_ref)) {
499 		ret = PTR_ERR(keyring_ref);
500 		goto error;
501 	}
502 
503 	key_ref = lookup_user_key(id, KEY_LOOKUP_FOR_UNLINK, 0);
504 	if (IS_ERR(key_ref)) {
505 		ret = PTR_ERR(key_ref);
506 		goto error2;
507 	}
508 
509 	ret = key_unlink(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));
510 
511 	key_ref_put(key_ref);
512 error2:
513 	key_ref_put(keyring_ref);
514 error:
515 	return ret;
516 }
517 
518 /*
519  * Return a description of a key to userspace.
520  *
521  * The key must grant the caller View permission for this to work.
522  *
523  * If there's a buffer, we place up to buflen bytes of data into it formatted
524  * in the following way:
525  *
526  *	type;uid;gid;perm;description<NUL>
527  *
528  * If successful, we return the amount of description available, irrespective
529  * of how much we may have copied into the buffer.
530  */
531 long keyctl_describe_key(key_serial_t keyid,
532 			 char __user *buffer,
533 			 size_t buflen)
534 {
535 	struct key *key, *instkey;
536 	key_ref_t key_ref;
537 	char *tmpbuf;
538 	long ret;
539 
540 	key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_VIEW);
541 	if (IS_ERR(key_ref)) {
542 		/* viewing a key under construction is permitted if we have the
543 		 * authorisation token handy */
544 		if (PTR_ERR(key_ref) == -EACCES) {
545 			instkey = key_get_instantiation_authkey(keyid);
546 			if (!IS_ERR(instkey)) {
547 				key_put(instkey);
548 				key_ref = lookup_user_key(keyid,
549 							  KEY_LOOKUP_PARTIAL,
550 							  0);
551 				if (!IS_ERR(key_ref))
552 					goto okay;
553 			}
554 		}
555 
556 		ret = PTR_ERR(key_ref);
557 		goto error;
558 	}
559 
560 okay:
561 	/* calculate how much description we're going to return */
562 	ret = -ENOMEM;
563 	tmpbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
564 	if (!tmpbuf)
565 		goto error2;
566 
567 	key = key_ref_to_ptr(key_ref);
568 
569 	ret = snprintf(tmpbuf, PAGE_SIZE - 1,
570 		       "%s;%d;%d;%08x;%s",
571 		       key->type->name,
572 		       key->uid,
573 		       key->gid,
574 		       key->perm,
575 		       key->description ?: "");
576 
577 	/* include a NUL char at the end of the data */
578 	if (ret > PAGE_SIZE - 1)
579 		ret = PAGE_SIZE - 1;
580 	tmpbuf[ret] = 0;
581 	ret++;
582 
583 	/* consider returning the data */
584 	if (buffer && buflen > 0) {
585 		if (buflen > ret)
586 			buflen = ret;
587 
588 		if (copy_to_user(buffer, tmpbuf, buflen) != 0)
589 			ret = -EFAULT;
590 	}
591 
592 	kfree(tmpbuf);
593 error2:
594 	key_ref_put(key_ref);
595 error:
596 	return ret;
597 }
598 
599 /*
600  * Search the specified keyring and any keyrings it links to for a matching
601  * key.  Only keyrings that grant the caller Search permission will be searched
602  * (this includes the starting keyring).  Only keys with Search permission can
603  * be found.
604  *
605  * If successful, the found key will be linked to the destination keyring if
606  * supplied and the key has Link permission, and the found key ID will be
607  * returned.
608  */
609 long keyctl_keyring_search(key_serial_t ringid,
610 			   const char __user *_type,
611 			   const char __user *_description,
612 			   key_serial_t destringid)
613 {
614 	struct key_type *ktype;
615 	key_ref_t keyring_ref, key_ref, dest_ref;
616 	char type[32], *description;
617 	long ret;
618 
619 	/* pull the type and description into kernel space */
620 	ret = key_get_type_from_user(type, _type, sizeof(type));
621 	if (ret < 0)
622 		goto error;
623 
624 	description = strndup_user(_description, PAGE_SIZE);
625 	if (IS_ERR(description)) {
626 		ret = PTR_ERR(description);
627 		goto error;
628 	}
629 
630 	/* get the keyring at which to begin the search */
631 	keyring_ref = lookup_user_key(ringid, 0, KEY_SEARCH);
632 	if (IS_ERR(keyring_ref)) {
633 		ret = PTR_ERR(keyring_ref);
634 		goto error2;
635 	}
636 
637 	/* get the destination keyring if specified */
638 	dest_ref = NULL;
639 	if (destringid) {
640 		dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
641 					   KEY_WRITE);
642 		if (IS_ERR(dest_ref)) {
643 			ret = PTR_ERR(dest_ref);
644 			goto error3;
645 		}
646 	}
647 
648 	/* find the key type */
649 	ktype = key_type_lookup(type);
650 	if (IS_ERR(ktype)) {
651 		ret = PTR_ERR(ktype);
652 		goto error4;
653 	}
654 
655 	/* do the search */
656 	key_ref = keyring_search(keyring_ref, ktype, description);
657 	if (IS_ERR(key_ref)) {
658 		ret = PTR_ERR(key_ref);
659 
660 		/* treat lack or presence of a negative key the same */
661 		if (ret == -EAGAIN)
662 			ret = -ENOKEY;
663 		goto error5;
664 	}
665 
666 	/* link the resulting key to the destination keyring if we can */
667 	if (dest_ref) {
668 		ret = key_permission(key_ref, KEY_LINK);
669 		if (ret < 0)
670 			goto error6;
671 
672 		ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));
673 		if (ret < 0)
674 			goto error6;
675 	}
676 
677 	ret = key_ref_to_ptr(key_ref)->serial;
678 
679 error6:
680 	key_ref_put(key_ref);
681 error5:
682 	key_type_put(ktype);
683 error4:
684 	key_ref_put(dest_ref);
685 error3:
686 	key_ref_put(keyring_ref);
687 error2:
688 	kfree(description);
689 error:
690 	return ret;
691 }
692 
693 /*
694  * Read a key's payload.
695  *
696  * The key must either grant the caller Read permission, or it must grant the
697  * caller Search permission when searched for from the process keyrings.
698  *
699  * If successful, we place up to buflen bytes of data into the buffer, if one
700  * is provided, and return the amount of data that is available in the key,
701  * irrespective of how much we copied into the buffer.
702  */
703 long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
704 {
705 	struct key *key;
706 	key_ref_t key_ref;
707 	long ret;
708 
709 	/* find the key first */
710 	key_ref = lookup_user_key(keyid, 0, 0);
711 	if (IS_ERR(key_ref)) {
712 		ret = -ENOKEY;
713 		goto error;
714 	}
715 
716 	key = key_ref_to_ptr(key_ref);
717 
718 	/* see if we can read it directly */
719 	ret = key_permission(key_ref, KEY_READ);
720 	if (ret == 0)
721 		goto can_read_key;
722 	if (ret != -EACCES)
723 		goto error;
724 
725 	/* we can't; see if it's searchable from this process's keyrings
726 	 * - we automatically take account of the fact that it may be
727 	 *   dangling off an instantiation key
728 	 */
729 	if (!is_key_possessed(key_ref)) {
730 		ret = -EACCES;
731 		goto error2;
732 	}
733 
734 	/* the key is probably readable - now try to read it */
735 can_read_key:
736 	ret = key_validate(key);
737 	if (ret == 0) {
738 		ret = -EOPNOTSUPP;
739 		if (key->type->read) {
740 			/* read the data with the semaphore held (since we
741 			 * might sleep) */
742 			down_read(&key->sem);
743 			ret = key->type->read(key, buffer, buflen);
744 			up_read(&key->sem);
745 		}
746 	}
747 
748 error2:
749 	key_put(key);
750 error:
751 	return ret;
752 }
753 
754 /*
755  * Change the ownership of a key
756  *
757  * The key must grant the caller Setattr permission for this to work, though
758  * the key need not be fully instantiated yet.  For the UID to be changed, or
759  * for the GID to be changed to a group the caller is not a member of, the
760  * caller must have sysadmin capability.  If either uid or gid is -1 then that
761  * attribute is not changed.
762  *
763  * If the UID is to be changed, the new user must have sufficient quota to
764  * accept the key.  The quota deduction will be removed from the old user to
765  * the new user should the attribute be changed.
766  *
767  * If successful, 0 will be returned.
768  */
769 long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
770 {
771 	struct key_user *newowner, *zapowner = NULL;
772 	struct key *key;
773 	key_ref_t key_ref;
774 	long ret;
775 
776 	ret = 0;
777 	if (uid == (uid_t) -1 && gid == (gid_t) -1)
778 		goto error;
779 
780 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
781 				  KEY_SETATTR);
782 	if (IS_ERR(key_ref)) {
783 		ret = PTR_ERR(key_ref);
784 		goto error;
785 	}
786 
787 	key = key_ref_to_ptr(key_ref);
788 
789 	/* make the changes with the locks held to prevent chown/chown races */
790 	ret = -EACCES;
791 	down_write(&key->sem);
792 
793 	if (!capable(CAP_SYS_ADMIN)) {
794 		/* only the sysadmin can chown a key to some other UID */
795 		if (uid != (uid_t) -1 && key->uid != uid)
796 			goto error_put;
797 
798 		/* only the sysadmin can set the key's GID to a group other
799 		 * than one of those that the current process subscribes to */
800 		if (gid != (gid_t) -1 && gid != key->gid && !in_group_p(gid))
801 			goto error_put;
802 	}
803 
804 	/* change the UID */
805 	if (uid != (uid_t) -1 && uid != key->uid) {
806 		ret = -ENOMEM;
807 		newowner = key_user_lookup(uid, current_user_ns());
808 		if (!newowner)
809 			goto error_put;
810 
811 		/* transfer the quota burden to the new user */
812 		if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
813 			unsigned maxkeys = (uid == 0) ?
814 				key_quota_root_maxkeys : key_quota_maxkeys;
815 			unsigned maxbytes = (uid == 0) ?
816 				key_quota_root_maxbytes : key_quota_maxbytes;
817 
818 			spin_lock(&newowner->lock);
819 			if (newowner->qnkeys + 1 >= maxkeys ||
820 			    newowner->qnbytes + key->quotalen >= maxbytes ||
821 			    newowner->qnbytes + key->quotalen <
822 			    newowner->qnbytes)
823 				goto quota_overrun;
824 
825 			newowner->qnkeys++;
826 			newowner->qnbytes += key->quotalen;
827 			spin_unlock(&newowner->lock);
828 
829 			spin_lock(&key->user->lock);
830 			key->user->qnkeys--;
831 			key->user->qnbytes -= key->quotalen;
832 			spin_unlock(&key->user->lock);
833 		}
834 
835 		atomic_dec(&key->user->nkeys);
836 		atomic_inc(&newowner->nkeys);
837 
838 		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
839 			atomic_dec(&key->user->nikeys);
840 			atomic_inc(&newowner->nikeys);
841 		}
842 
843 		zapowner = key->user;
844 		key->user = newowner;
845 		key->uid = uid;
846 	}
847 
848 	/* change the GID */
849 	if (gid != (gid_t) -1)
850 		key->gid = gid;
851 
852 	ret = 0;
853 
854 error_put:
855 	up_write(&key->sem);
856 	key_put(key);
857 	if (zapowner)
858 		key_user_put(zapowner);
859 error:
860 	return ret;
861 
862 quota_overrun:
863 	spin_unlock(&newowner->lock);
864 	zapowner = newowner;
865 	ret = -EDQUOT;
866 	goto error_put;
867 }
868 
869 /*
870  * Change the permission mask on a key.
871  *
872  * The key must grant the caller Setattr permission for this to work, though
873  * the key need not be fully instantiated yet.  If the caller does not have
874  * sysadmin capability, it may only change the permission on keys that it owns.
875  */
876 long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
877 {
878 	struct key *key;
879 	key_ref_t key_ref;
880 	long ret;
881 
882 	ret = -EINVAL;
883 	if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
884 		goto error;
885 
886 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
887 				  KEY_SETATTR);
888 	if (IS_ERR(key_ref)) {
889 		ret = PTR_ERR(key_ref);
890 		goto error;
891 	}
892 
893 	key = key_ref_to_ptr(key_ref);
894 
895 	/* make the changes with the locks held to prevent chown/chmod races */
896 	ret = -EACCES;
897 	down_write(&key->sem);
898 
899 	/* if we're not the sysadmin, we can only change a key that we own */
900 	if (capable(CAP_SYS_ADMIN) || key->uid == current_fsuid()) {
901 		key->perm = perm;
902 		ret = 0;
903 	}
904 
905 	up_write(&key->sem);
906 	key_put(key);
907 error:
908 	return ret;
909 }
910 
911 /*
912  * Get the destination keyring for instantiation and check that the caller has
913  * Write permission on it.
914  */
915 static long get_instantiation_keyring(key_serial_t ringid,
916 				      struct request_key_auth *rka,
917 				      struct key **_dest_keyring)
918 {
919 	key_ref_t dkref;
920 
921 	*_dest_keyring = NULL;
922 
923 	/* just return a NULL pointer if we weren't asked to make a link */
924 	if (ringid == 0)
925 		return 0;
926 
927 	/* if a specific keyring is nominated by ID, then use that */
928 	if (ringid > 0) {
929 		dkref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
930 		if (IS_ERR(dkref))
931 			return PTR_ERR(dkref);
932 		*_dest_keyring = key_ref_to_ptr(dkref);
933 		return 0;
934 	}
935 
936 	if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
937 		return -EINVAL;
938 
939 	/* otherwise specify the destination keyring recorded in the
940 	 * authorisation key (any KEY_SPEC_*_KEYRING) */
941 	if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {
942 		*_dest_keyring = key_get(rka->dest_keyring);
943 		return 0;
944 	}
945 
946 	return -ENOKEY;
947 }
948 
949 /*
950  * Change the request_key authorisation key on the current process.
951  */
952 static int keyctl_change_reqkey_auth(struct key *key)
953 {
954 	struct cred *new;
955 
956 	new = prepare_creds();
957 	if (!new)
958 		return -ENOMEM;
959 
960 	key_put(new->request_key_auth);
961 	new->request_key_auth = key_get(key);
962 
963 	return commit_creds(new);
964 }
965 
966 /*
967  * Copy the iovec data from userspace
968  */
969 static long copy_from_user_iovec(void *buffer, const struct iovec *iov,
970 				 unsigned ioc)
971 {
972 	for (; ioc > 0; ioc--) {
973 		if (copy_from_user(buffer, iov->iov_base, iov->iov_len) != 0)
974 			return -EFAULT;
975 		buffer += iov->iov_len;
976 		iov++;
977 	}
978 	return 0;
979 }
980 
981 /*
982  * Instantiate a key with the specified payload and link the key into the
983  * destination keyring if one is given.
984  *
985  * The caller must have the appropriate instantiation permit set for this to
986  * work (see keyctl_assume_authority).  No other permissions are required.
987  *
988  * If successful, 0 will be returned.
989  */
990 long keyctl_instantiate_key_common(key_serial_t id,
991 				   const struct iovec *payload_iov,
992 				   unsigned ioc,
993 				   size_t plen,
994 				   key_serial_t ringid)
995 {
996 	const struct cred *cred = current_cred();
997 	struct request_key_auth *rka;
998 	struct key *instkey, *dest_keyring;
999 	void *payload;
1000 	long ret;
1001 	bool vm = false;
1002 
1003 	kenter("%d,,%zu,%d", id, plen, ringid);
1004 
1005 	ret = -EINVAL;
1006 	if (plen > 1024 * 1024 - 1)
1007 		goto error;
1008 
1009 	/* the appropriate instantiation authorisation key must have been
1010 	 * assumed before calling this */
1011 	ret = -EPERM;
1012 	instkey = cred->request_key_auth;
1013 	if (!instkey)
1014 		goto error;
1015 
1016 	rka = instkey->payload.data;
1017 	if (rka->target_key->serial != id)
1018 		goto error;
1019 
1020 	/* pull the payload in if one was supplied */
1021 	payload = NULL;
1022 
1023 	if (payload_iov) {
1024 		ret = -ENOMEM;
1025 		payload = kmalloc(plen, GFP_KERNEL);
1026 		if (!payload) {
1027 			if (plen <= PAGE_SIZE)
1028 				goto error;
1029 			vm = true;
1030 			payload = vmalloc(plen);
1031 			if (!payload)
1032 				goto error;
1033 		}
1034 
1035 		ret = copy_from_user_iovec(payload, payload_iov, ioc);
1036 		if (ret < 0)
1037 			goto error2;
1038 	}
1039 
1040 	/* find the destination keyring amongst those belonging to the
1041 	 * requesting task */
1042 	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
1043 	if (ret < 0)
1044 		goto error2;
1045 
1046 	/* instantiate the key and link it into a keyring */
1047 	ret = key_instantiate_and_link(rka->target_key, payload, plen,
1048 				       dest_keyring, instkey);
1049 
1050 	key_put(dest_keyring);
1051 
1052 	/* discard the assumed authority if it's just been disabled by
1053 	 * instantiation of the key */
1054 	if (ret == 0)
1055 		keyctl_change_reqkey_auth(NULL);
1056 
1057 error2:
1058 	if (!vm)
1059 		kfree(payload);
1060 	else
1061 		vfree(payload);
1062 error:
1063 	return ret;
1064 }
1065 
1066 /*
1067  * Instantiate a key with the specified payload and link the key into the
1068  * destination keyring if one is given.
1069  *
1070  * The caller must have the appropriate instantiation permit set for this to
1071  * work (see keyctl_assume_authority).  No other permissions are required.
1072  *
1073  * If successful, 0 will be returned.
1074  */
1075 long keyctl_instantiate_key(key_serial_t id,
1076 			    const void __user *_payload,
1077 			    size_t plen,
1078 			    key_serial_t ringid)
1079 {
1080 	if (_payload && plen) {
1081 		struct iovec iov[1] = {
1082 			[0].iov_base = (void __user *)_payload,
1083 			[0].iov_len  = plen
1084 		};
1085 
1086 		return keyctl_instantiate_key_common(id, iov, 1, plen, ringid);
1087 	}
1088 
1089 	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
1090 }
1091 
1092 /*
1093  * Instantiate a key with the specified multipart payload and link the key into
1094  * the destination keyring if one is given.
1095  *
1096  * The caller must have the appropriate instantiation permit set for this to
1097  * work (see keyctl_assume_authority).  No other permissions are required.
1098  *
1099  * If successful, 0 will be returned.
1100  */
1101 long keyctl_instantiate_key_iov(key_serial_t id,
1102 				const struct iovec __user *_payload_iov,
1103 				unsigned ioc,
1104 				key_serial_t ringid)
1105 {
1106 	struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
1107 	long ret;
1108 
1109 	if (!_payload_iov || !ioc)
1110 		goto no_payload;
1111 
1112 	ret = rw_copy_check_uvector(WRITE, _payload_iov, ioc,
1113 				    ARRAY_SIZE(iovstack), iovstack, &iov);
1114 	if (ret < 0)
1115 		return ret;
1116 	if (ret == 0)
1117 		goto no_payload_free;
1118 
1119 	ret = keyctl_instantiate_key_common(id, iov, ioc, ret, ringid);
1120 
1121 	if (iov != iovstack)
1122 		kfree(iov);
1123 	return ret;
1124 
1125 no_payload_free:
1126 	if (iov != iovstack)
1127 		kfree(iov);
1128 no_payload:
1129 	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
1130 }
1131 
1132 /*
1133  * Negatively instantiate the key with the given timeout (in seconds) and link
1134  * the key into the destination keyring if one is given.
1135  *
1136  * The caller must have the appropriate instantiation permit set for this to
1137  * work (see keyctl_assume_authority).  No other permissions are required.
1138  *
1139  * The key and any links to the key will be automatically garbage collected
1140  * after the timeout expires.
1141  *
1142  * Negative keys are used to rate limit repeated request_key() calls by causing
1143  * them to return -ENOKEY until the negative key expires.
1144  *
1145  * If successful, 0 will be returned.
1146  */
1147 long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
1148 {
1149 	return keyctl_reject_key(id, timeout, ENOKEY, ringid);
1150 }
1151 
1152 /*
1153  * Negatively instantiate the key with the given timeout (in seconds) and error
1154  * code and link the key into the destination keyring if one is given.
1155  *
1156  * The caller must have the appropriate instantiation permit set for this to
1157  * work (see keyctl_assume_authority).  No other permissions are required.
1158  *
1159  * The key and any links to the key will be automatically garbage collected
1160  * after the timeout expires.
1161  *
1162  * Negative keys are used to rate limit repeated request_key() calls by causing
1163  * them to return the specified error code until the negative key expires.
1164  *
1165  * If successful, 0 will be returned.
1166  */
1167 long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
1168 		       key_serial_t ringid)
1169 {
1170 	const struct cred *cred = current_cred();
1171 	struct request_key_auth *rka;
1172 	struct key *instkey, *dest_keyring;
1173 	long ret;
1174 
1175 	kenter("%d,%u,%u,%d", id, timeout, error, ringid);
1176 
1177 	/* must be a valid error code and mustn't be a kernel special */
1178 	if (error <= 0 ||
1179 	    error >= MAX_ERRNO ||
1180 	    error == ERESTARTSYS ||
1181 	    error == ERESTARTNOINTR ||
1182 	    error == ERESTARTNOHAND ||
1183 	    error == ERESTART_RESTARTBLOCK)
1184 		return -EINVAL;
1185 
1186 	/* the appropriate instantiation authorisation key must have been
1187 	 * assumed before calling this */
1188 	ret = -EPERM;
1189 	instkey = cred->request_key_auth;
1190 	if (!instkey)
1191 		goto error;
1192 
1193 	rka = instkey->payload.data;
1194 	if (rka->target_key->serial != id)
1195 		goto error;
1196 
1197 	/* find the destination keyring if present (which must also be
1198 	 * writable) */
1199 	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
1200 	if (ret < 0)
1201 		goto error;
1202 
1203 	/* instantiate the key and link it into a keyring */
1204 	ret = key_reject_and_link(rka->target_key, timeout, error,
1205 				  dest_keyring, instkey);
1206 
1207 	key_put(dest_keyring);
1208 
1209 	/* discard the assumed authority if it's just been disabled by
1210 	 * instantiation of the key */
1211 	if (ret == 0)
1212 		keyctl_change_reqkey_auth(NULL);
1213 
1214 error:
1215 	return ret;
1216 }
1217 
1218 /*
1219  * Read or set the default keyring in which request_key() will cache keys and
1220  * return the old setting.
1221  *
1222  * If a process keyring is specified then this will be created if it doesn't
1223  * yet exist.  The old setting will be returned if successful.
1224  */
1225 long keyctl_set_reqkey_keyring(int reqkey_defl)
1226 {
1227 	struct cred *new;
1228 	int ret, old_setting;
1229 
1230 	old_setting = current_cred_xxx(jit_keyring);
1231 
1232 	if (reqkey_defl == KEY_REQKEY_DEFL_NO_CHANGE)
1233 		return old_setting;
1234 
1235 	new = prepare_creds();
1236 	if (!new)
1237 		return -ENOMEM;
1238 
1239 	switch (reqkey_defl) {
1240 	case KEY_REQKEY_DEFL_THREAD_KEYRING:
1241 		ret = install_thread_keyring_to_cred(new);
1242 		if (ret < 0)
1243 			goto error;
1244 		goto set;
1245 
1246 	case KEY_REQKEY_DEFL_PROCESS_KEYRING:
1247 		ret = install_process_keyring_to_cred(new);
1248 		if (ret < 0) {
1249 			if (ret != -EEXIST)
1250 				goto error;
1251 			ret = 0;
1252 		}
1253 		goto set;
1254 
1255 	case KEY_REQKEY_DEFL_DEFAULT:
1256 	case KEY_REQKEY_DEFL_SESSION_KEYRING:
1257 	case KEY_REQKEY_DEFL_USER_KEYRING:
1258 	case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
1259 	case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
1260 		goto set;
1261 
1262 	case KEY_REQKEY_DEFL_NO_CHANGE:
1263 	case KEY_REQKEY_DEFL_GROUP_KEYRING:
1264 	default:
1265 		ret = -EINVAL;
1266 		goto error;
1267 	}
1268 
1269 set:
1270 	new->jit_keyring = reqkey_defl;
1271 	commit_creds(new);
1272 	return old_setting;
1273 error:
1274 	abort_creds(new);
1275 	return ret;
1276 }
1277 
1278 /*
1279  * Set or clear the timeout on a key.
1280  *
1281  * Either the key must grant the caller Setattr permission or else the caller
1282  * must hold an instantiation authorisation token for the key.
1283  *
1284  * The timeout is either 0 to clear the timeout, or a number of seconds from
1285  * the current time.  The key and any links to the key will be automatically
1286  * garbage collected after the timeout expires.
1287  *
1288  * If successful, 0 is returned.
1289  */
1290 long keyctl_set_timeout(key_serial_t id, unsigned timeout)
1291 {
1292 	struct key *key, *instkey;
1293 	key_ref_t key_ref;
1294 	long ret;
1295 
1296 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
1297 				  KEY_SETATTR);
1298 	if (IS_ERR(key_ref)) {
1299 		/* setting the timeout on a key under construction is permitted
1300 		 * if we have the authorisation token handy */
1301 		if (PTR_ERR(key_ref) == -EACCES) {
1302 			instkey = key_get_instantiation_authkey(id);
1303 			if (!IS_ERR(instkey)) {
1304 				key_put(instkey);
1305 				key_ref = lookup_user_key(id,
1306 							  KEY_LOOKUP_PARTIAL,
1307 							  0);
1308 				if (!IS_ERR(key_ref))
1309 					goto okay;
1310 			}
1311 		}
1312 
1313 		ret = PTR_ERR(key_ref);
1314 		goto error;
1315 	}
1316 
1317 okay:
1318 	key = key_ref_to_ptr(key_ref);
1319 	key_set_timeout(key, timeout);
1320 	key_put(key);
1321 
1322 	ret = 0;
1323 error:
1324 	return ret;
1325 }
1326 
1327 /*
1328  * Assume (or clear) the authority to instantiate the specified key.
1329  *
1330  * This sets the authoritative token currently in force for key instantiation.
1331  * This must be done for a key to be instantiated.  It has the effect of making
1332  * available all the keys from the caller of the request_key() that created a
1333  * key to request_key() calls made by the caller of this function.
1334  *
1335  * The caller must have the instantiation key in their process keyrings with a
1336  * Search permission grant available to the caller.
1337  *
1338  * If the ID given is 0, then the setting will be cleared and 0 returned.
1339  *
1340  * If the ID given has a matching an authorisation key, then that key will be
1341  * set and its ID will be returned.  The authorisation key can be read to get
1342  * the callout information passed to request_key().
1343  */
1344 long keyctl_assume_authority(key_serial_t id)
1345 {
1346 	struct key *authkey;
1347 	long ret;
1348 
1349 	/* special key IDs aren't permitted */
1350 	ret = -EINVAL;
1351 	if (id < 0)
1352 		goto error;
1353 
1354 	/* we divest ourselves of authority if given an ID of 0 */
1355 	if (id == 0) {
1356 		ret = keyctl_change_reqkey_auth(NULL);
1357 		goto error;
1358 	}
1359 
1360 	/* attempt to assume the authority temporarily granted to us whilst we
1361 	 * instantiate the specified key
1362 	 * - the authorisation key must be in the current task's keyrings
1363 	 *   somewhere
1364 	 */
1365 	authkey = key_get_instantiation_authkey(id);
1366 	if (IS_ERR(authkey)) {
1367 		ret = PTR_ERR(authkey);
1368 		goto error;
1369 	}
1370 
1371 	ret = keyctl_change_reqkey_auth(authkey);
1372 	if (ret < 0)
1373 		goto error;
1374 	key_put(authkey);
1375 
1376 	ret = authkey->serial;
1377 error:
1378 	return ret;
1379 }
1380 
1381 /*
1382  * Get a key's the LSM security label.
1383  *
1384  * The key must grant the caller View permission for this to work.
1385  *
1386  * If there's a buffer, then up to buflen bytes of data will be placed into it.
1387  *
1388  * If successful, the amount of information available will be returned,
1389  * irrespective of how much was copied (including the terminal NUL).
1390  */
1391 long keyctl_get_security(key_serial_t keyid,
1392 			 char __user *buffer,
1393 			 size_t buflen)
1394 {
1395 	struct key *key, *instkey;
1396 	key_ref_t key_ref;
1397 	char *context;
1398 	long ret;
1399 
1400 	key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_VIEW);
1401 	if (IS_ERR(key_ref)) {
1402 		if (PTR_ERR(key_ref) != -EACCES)
1403 			return PTR_ERR(key_ref);
1404 
1405 		/* viewing a key under construction is also permitted if we
1406 		 * have the authorisation token handy */
1407 		instkey = key_get_instantiation_authkey(keyid);
1408 		if (IS_ERR(instkey))
1409 			return PTR_ERR(instkey);
1410 		key_put(instkey);
1411 
1412 		key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, 0);
1413 		if (IS_ERR(key_ref))
1414 			return PTR_ERR(key_ref);
1415 	}
1416 
1417 	key = key_ref_to_ptr(key_ref);
1418 	ret = security_key_getsecurity(key, &context);
1419 	if (ret == 0) {
1420 		/* if no information was returned, give userspace an empty
1421 		 * string */
1422 		ret = 1;
1423 		if (buffer && buflen > 0 &&
1424 		    copy_to_user(buffer, "", 1) != 0)
1425 			ret = -EFAULT;
1426 	} else if (ret > 0) {
1427 		/* return as much data as there's room for */
1428 		if (buffer && buflen > 0) {
1429 			if (buflen > ret)
1430 				buflen = ret;
1431 
1432 			if (copy_to_user(buffer, context, buflen) != 0)
1433 				ret = -EFAULT;
1434 		}
1435 
1436 		kfree(context);
1437 	}
1438 
1439 	key_ref_put(key_ref);
1440 	return ret;
1441 }
1442 
1443 /*
1444  * Attempt to install the calling process's session keyring on the process's
1445  * parent process.
1446  *
1447  * The keyring must exist and must grant the caller LINK permission, and the
1448  * parent process must be single-threaded and must have the same effective
1449  * ownership as this process and mustn't be SUID/SGID.
1450  *
1451  * The keyring will be emplaced on the parent when it next resumes userspace.
1452  *
1453  * If successful, 0 will be returned.
1454  */
1455 long keyctl_session_to_parent(void)
1456 {
1457 	struct task_struct *me, *parent;
1458 	const struct cred *mycred, *pcred;
1459 	struct callback_head *newwork, *oldwork;
1460 	key_ref_t keyring_r;
1461 	struct cred *cred;
1462 	int ret;
1463 
1464 	keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_LINK);
1465 	if (IS_ERR(keyring_r))
1466 		return PTR_ERR(keyring_r);
1467 
1468 	ret = -ENOMEM;
1469 
1470 	/* our parent is going to need a new cred struct, a new tgcred struct
1471 	 * and new security data, so we allocate them here to prevent ENOMEM in
1472 	 * our parent */
1473 	cred = cred_alloc_blank();
1474 	if (!cred)
1475 		goto error_keyring;
1476 	newwork = &cred->rcu;
1477 
1478 	cred->tgcred->session_keyring = key_ref_to_ptr(keyring_r);
1479 	init_task_work(newwork, key_change_session_keyring);
1480 
1481 	me = current;
1482 	rcu_read_lock();
1483 	write_lock_irq(&tasklist_lock);
1484 
1485 	ret = -EPERM;
1486 	oldwork = NULL;
1487 	parent = me->real_parent;
1488 
1489 	task_lock(parent);
1490 	/* the parent mustn't be init and mustn't be a kernel thread */
1491 	if (parent->pid <= 1 || !parent->mm)
1492 		goto unlock;
1493 
1494 	/* the parent must be single threaded */
1495 	if (!thread_group_empty(parent))
1496 		goto unlock;
1497 
1498 	/* the parent and the child must have different session keyrings or
1499 	 * there's no point */
1500 	mycred = current_cred();
1501 	pcred = __task_cred(parent);
1502 	if (mycred == pcred ||
1503 	    mycred->tgcred->session_keyring == pcred->tgcred->session_keyring) {
1504 		ret = 0;
1505 		goto unlock;
1506 	}
1507 
1508 	/* the parent must have the same effective ownership and mustn't be
1509 	 * SUID/SGID */
1510 	if (pcred->uid	!= mycred->euid	||
1511 	    pcred->euid	!= mycred->euid	||
1512 	    pcred->suid	!= mycred->euid	||
1513 	    pcred->gid	!= mycred->egid	||
1514 	    pcred->egid	!= mycred->egid	||
1515 	    pcred->sgid	!= mycred->egid)
1516 		goto unlock;
1517 
1518 	/* the keyrings must have the same UID */
1519 	if ((pcred->tgcred->session_keyring &&
1520 	     pcred->tgcred->session_keyring->uid != mycred->euid) ||
1521 	    mycred->tgcred->session_keyring->uid != mycred->euid)
1522 		goto unlock;
1523 
1524 	/* cancel an already pending keyring replacement */
1525 	oldwork = task_work_cancel(parent, key_change_session_keyring);
1526 
1527 	/* the replacement session keyring is applied just prior to userspace
1528 	 * restarting */
1529 	ret = task_work_add(parent, newwork, true);
1530 	if (!ret)
1531 		newwork = NULL;
1532 unlock:
1533 	task_unlock(parent);
1534 	write_unlock_irq(&tasklist_lock);
1535 	rcu_read_unlock();
1536 	if (oldwork)
1537 		put_cred(container_of(oldwork, struct cred, rcu));
1538 	if (newwork)
1539 		put_cred(cred);
1540 	return ret;
1541 
1542 error_keyring:
1543 	key_ref_put(keyring_r);
1544 	return ret;
1545 }
1546 
1547 /*
1548  * The key control system call
1549  */
1550 SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
1551 		unsigned long, arg4, unsigned long, arg5)
1552 {
1553 	switch (option) {
1554 	case KEYCTL_GET_KEYRING_ID:
1555 		return keyctl_get_keyring_ID((key_serial_t) arg2,
1556 					     (int) arg3);
1557 
1558 	case KEYCTL_JOIN_SESSION_KEYRING:
1559 		return keyctl_join_session_keyring((const char __user *) arg2);
1560 
1561 	case KEYCTL_UPDATE:
1562 		return keyctl_update_key((key_serial_t) arg2,
1563 					 (const void __user *) arg3,
1564 					 (size_t) arg4);
1565 
1566 	case KEYCTL_REVOKE:
1567 		return keyctl_revoke_key((key_serial_t) arg2);
1568 
1569 	case KEYCTL_DESCRIBE:
1570 		return keyctl_describe_key((key_serial_t) arg2,
1571 					   (char __user *) arg3,
1572 					   (unsigned) arg4);
1573 
1574 	case KEYCTL_CLEAR:
1575 		return keyctl_keyring_clear((key_serial_t) arg2);
1576 
1577 	case KEYCTL_LINK:
1578 		return keyctl_keyring_link((key_serial_t) arg2,
1579 					   (key_serial_t) arg3);
1580 
1581 	case KEYCTL_UNLINK:
1582 		return keyctl_keyring_unlink((key_serial_t) arg2,
1583 					     (key_serial_t) arg3);
1584 
1585 	case KEYCTL_SEARCH:
1586 		return keyctl_keyring_search((key_serial_t) arg2,
1587 					     (const char __user *) arg3,
1588 					     (const char __user *) arg4,
1589 					     (key_serial_t) arg5);
1590 
1591 	case KEYCTL_READ:
1592 		return keyctl_read_key((key_serial_t) arg2,
1593 				       (char __user *) arg3,
1594 				       (size_t) arg4);
1595 
1596 	case KEYCTL_CHOWN:
1597 		return keyctl_chown_key((key_serial_t) arg2,
1598 					(uid_t) arg3,
1599 					(gid_t) arg4);
1600 
1601 	case KEYCTL_SETPERM:
1602 		return keyctl_setperm_key((key_serial_t) arg2,
1603 					  (key_perm_t) arg3);
1604 
1605 	case KEYCTL_INSTANTIATE:
1606 		return keyctl_instantiate_key((key_serial_t) arg2,
1607 					      (const void __user *) arg3,
1608 					      (size_t) arg4,
1609 					      (key_serial_t) arg5);
1610 
1611 	case KEYCTL_NEGATE:
1612 		return keyctl_negate_key((key_serial_t) arg2,
1613 					 (unsigned) arg3,
1614 					 (key_serial_t) arg4);
1615 
1616 	case KEYCTL_SET_REQKEY_KEYRING:
1617 		return keyctl_set_reqkey_keyring(arg2);
1618 
1619 	case KEYCTL_SET_TIMEOUT:
1620 		return keyctl_set_timeout((key_serial_t) arg2,
1621 					  (unsigned) arg3);
1622 
1623 	case KEYCTL_ASSUME_AUTHORITY:
1624 		return keyctl_assume_authority((key_serial_t) arg2);
1625 
1626 	case KEYCTL_GET_SECURITY:
1627 		return keyctl_get_security((key_serial_t) arg2,
1628 					   (char __user *) arg3,
1629 					   (size_t) arg4);
1630 
1631 	case KEYCTL_SESSION_TO_PARENT:
1632 		return keyctl_session_to_parent();
1633 
1634 	case KEYCTL_REJECT:
1635 		return keyctl_reject_key((key_serial_t) arg2,
1636 					 (unsigned) arg3,
1637 					 (unsigned) arg4,
1638 					 (key_serial_t) arg5);
1639 
1640 	case KEYCTL_INSTANTIATE_IOV:
1641 		return keyctl_instantiate_key_iov(
1642 			(key_serial_t) arg2,
1643 			(const struct iovec __user *) arg3,
1644 			(unsigned) arg4,
1645 			(key_serial_t) arg5);
1646 
1647 	case KEYCTL_INVALIDATE:
1648 		return keyctl_invalidate_key((key_serial_t) arg2);
1649 
1650 	default:
1651 		return -EOPNOTSUPP;
1652 	}
1653 }
1654